The studies to be outlined in this proposal deal with fibrinogen immunochemistry, particularly with the immunochemistry of structurally well-characterized fragments which have been shown to be of functional importance in the molecule as regards hemostasis. The long term goal of this research is understanding the structure and function of the fibrinogen molecule and of the processes that lead to its transformation into fibrin. The study is also expected to provide basic information concerning the structural requirements for eliciting an immune response. Specifically, we intend to: 1. Characterize the structure and location of epitopes on functionally important fragments of fibrinogen. 2. Study the immunological differences between N-DSK from fibrinogen and N-DSK of fibrinogen. This investigation will also include a study of the conformational perturbation associated with release of fibrinopeptides A and B from N-DSK. N-DSK from normal as well as abnormal fibrinogens will be studied. 3. Study polymorphism in chains of human fibrinogen.